Hey Gail - I know you didn't ask me, and frankly, I don't know much. So I sure hope Chip answers your question. But I can share my personal
experience. When my hybrid mountain/road bike got stolen years ago, I didn't bother to replace it because riding it caused so much back pain (not a herniated disk, but nerve impingement). But as time went by I wanted to be able to ride with my kids. It happened that I was able to use airline frequent flier miles (I was in a job that required travel at the time) to get a really good deal on a Trek bike that is very similar to their current Shift model.
http://www.trekbikes.com/us/en/bikes/town/recreation/shift_comfort/ The seat is slightly behind, not directly over the pedals, and the handlebars are above the seat. I was amazed at the difference. The natural, upright posture causes absolutely no problems for me at all.
I don't know what will work for you, but offering this in case it helps.